She'd gone in for back surgery.

Maureen Pacheco, now 53, arrived at a hospital in April 2016 for a procedure to fuse a few of the vertebrae in her lower spine to help reduce back pain. She left missing a kidney.

Her surgeon at Wellington Regional Medical Center in Wellington, Fla. took it out assuming the mass in her pelvis was a cancerous tumour, the Washington Post reported.

"As you can imagine, when someone goes in for a back surgery, she would never expect to wake up and be told when she's just waking up from anesthesia, that one of her kidneys has been unnecessarily removed," her lawyer, Donald Ward, told the Palm Beach Post.

'Medically negligent'

Pacheco had a pelvic kidney on her left side — a fully-functioning organ that never rose into the right spot in her abdomen when she was developing as a fetus. Prior to her surgery, she had undergone two MRIs which indicated the unusual positioning. The surgeon responsible, Ramon Vazquez, did not look at the MRIs, and was allegedly only in the operating room to cut her open for the other two surgeons in the room, not perform the back surgery.

She sued Vazquez last year arguing that he was "medically negligent." The lawsuit was settled for an undisclosed amount, but his lawyer told the Post that he did not admit liability and that Vazquez "does not think he did anything wrong."

The surgeon blamed the hospital for not informing him about Pacheco's pelvic kidney.

"I wish no ill will against him. Everyone is entitled to their livelihood but you should have consequences when gross mistakes and negligence are made," Pacheco told Tribune Media Wire. "I just wish that he learns a lesson from the consequences."

As you can imagine, when someone goes in for a back surgery, she would never expect to wake up and be told when she's just waking up from anesthesia, that one of her kidneys has been unnecessarily removed.Donald Ward

Vazquez, an independent physician, had no disciplinary record on file in Florida prior to the incident, but is no longer working at Wellington Regional, the hospital said in a statement.

"Wellington Regional took all necessary and appropriate steps to review the circumstances of this most unfortunate incident. In the over-30-year history of Wellington Regional Medical Center, an incident of this nature has never occurred before or since," the statement says according to People.

The Florida Health Department filed a complaint against Vazquez and requested that the state's Board of Medicine revoke or suspend his licence, put him on probation or fine him for the "unauthorized procedure."

Most people can live normally with just one working kidney, though having two puts less strain on the body.